The new Dynamic Light Scattering (DLS) Clinical device has recently been developed under the NASA-NEI Inter-Agency Agreement, and has been found to be safe, reproducible and sensitive to use in studies of early cataract formation. It can detect the earliest molecular changes in cataracts in patients in vivo, non-invasively. In this pilot study, we will be using this new device to study the earliest changes in cataract formation, in the molecular level, in patients with Pre-Senile cataract. These cataracts develop in patients below the age of 55 years of age (hence"Pre-Senile"), and these cataracts develop rapidly in the first eye, requiring surgery within a year or two. The other eye usually develops a similar rapidly developing cataract after the first eye, and therefore can be studied from the start with this device. This study will hopefully help elucidate, in the molecular level, what happens in the earliest stages of cataract formation in this type of human cataract, and help us follow the cascade of events that occur after the initial changes. This information will be useful in finding the cause of human cataracts and may lead to development of "counter- measures" such as anti-cataract medications, that may prevent, delay or reverse cataracts medically/ non-surgically. Preliminary data shows that very early changes in lens proteins can be detected even in the clinically uninvolved contralateral eye. We are therefore continuing to follow these patients after the ipsilateral, cataractous eye had been operated on. This type of study has not been possible in the past because no clinical device has been developed to study molecular changes in the lens safely, reproducibly and non-invasively in vivo, with the lens in-situ, without taking the lens outside of the eye.